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.Dd July 21, 2003
.Dt PMAP_EXTRACT 9
.Os
.Sh NAME
.Nm pmap_extract ,
.Nm pmap_extract_and_hold
.Nd map a virtual address to a physical page
.Sh SYNOPSIS
.In sys/param.h
.In vm/vm.h
.In vm/pmap.h
.Ft vm_paddr_t
.Fn pmap_extract "pmap_t pmap" "vm_offset_t va"
.Ft vm_page_t
.Fn pmap_extract_and_hold "pmap_t pmap" "vm_offset_t va" "vm_prot_t prot"
.Sh DESCRIPTION
The
.Fn pmap_extract
function maps a virtual address to a physical page.
In certain situations, callers may use
.Fn pmap_extract_and_hold
instead, to ensure that the returned page is held.
.Pp
The
.Fn pmap_extract_and_hold
function maps a virtual address to a physical page, and atomically holds
the returned page for use by the caller, only if the mapping permits
the given page protection.
.Sh IMPLEMENTATION NOTES
Currently, the page protection requested by the caller is not verified.
.Sh RETURN VALUES
The
.Fn pmap_extract
function will return the physical page address associated with the
virtual address
.Fa va
inside the physical map
.Fa pmap .
If the mapping does not exist, or if the
.Fa pmap
parameter is
.Dv NULL ,
then
.Dv NULL
will be returned.
.Pp
The
.Fn pmap_extract_and_hold
function will return the
.Ft vm_page_t
associated with the
virtual address
.Fa va
inside the physical map
.Fa pmap .
If the mapping does not exist, the result is a no-op, and
.Dv NULL
will
be returned.
.Sh SEE ALSO
.Xr mutex 9 ,
.Xr pmap 9
.Sh AUTHORS
.An -nosplit
The
.Fn pmap_extract_and_hold
function was implemented by
.An Alan L. Cox Aq Mt alc@imimic.com .
This manual page was written by
.An Bruce M Simpson Aq Mt bms@spc.org .
